US 8171972 B2
Disclosed are examples of a strip guide for laterally shifting a longitudinally moving strip material as it enters a joining mechanism that urges the strip material into contact with a moving sheet material, the strip guide comprising a surface over which the strip material passes longitudinally, the surface defining a U-shape.
1. A strip guide for laterally shifting a longitudinally moving strip material as it enters a joining mechanism that urges the strip material into contact with a moving sheet material, the strip guide comprising a surface over which the strip material passes longitudinally, the surface defining a U-shape, wherein the U-shape has a curving portion that substantially comprises a semicircle having a radius, and the strip material has a strip width, and the radius of the semicircle is approximately 21 to approximately 43 percent of the strip width.
2. The strip guide of
3. The strip guide of
4. The strip guide of
5. The strip guide of
This invention relates to a system, components thereof, and method for continuously applying and affixing a strip material to a sheet-like substrate material moving longitudinally through a manufacturing line, at laterally shifting locations on the substrate material. More particularly, the present invention relates to a system and components that continuously draw respective strip material and sheet-like substrate material from continuous supplies, and laterally shift the strip material across the machine direction of the substrate material as the two materials enter a joining mechanism that affixes the strip material onto the substrate material. The invention also relates to a system, components thereof, and method for continuously regulating the strain in a longitudinal material as it enters a joining mechanism.
Currently, wearable articles such as disposable diapers, disposable training pants, disposable adult incontinence garments and the like are constructed of various types of sheet- or strip-like materials. These materials may include nonwoven webs formed of synthetic polymer and/or natural fibers (“nonwovens”), polymeric films, elastic strands, strips or sheets, or assemblies or laminates of these materials. In a typical article, nonwovens and/or laminates of various types form at least one component of an outer garment-facing layer (“backsheet”), an inner body-facing layer (“topsheet”) and various internal layers, cuffs, envelopes or other features, depending upon the particular features of the product. The component sheet- or strip-like materials are usually supplied in the form of large continuous rolls, or alternatively, boxes of continuous longitudinal sheet or strip material gathered and folded transversely in accordion fashion.
The articles are typically manufactured on relatively complex manufacturing lines. Supplies of the required materials are placed at the front of each line. As a line requires the materials for the manufacture of articles, it continuously draws the materials longitudinally from their respective supplies. As a particular material is drawn from the supply and proceeds through the line to be incorporated into final product, it may be flipped, shifted, folded, laminated, welded, stamped, embossed, bonded to other components, cut, etc., ultimately being fashioned by the machinery into an incorporated part of the finished product. All of this happens at the economically-required production rate, e.g., 450 or more product items per line per minute. Generally, for purposes of economy, increasing the production rate is an ever-present objective.
A new design for a wearable absorbent article such as a disposable diaper, training pant or adult incontinence undergarment has been developed. The article has features that give it an underwear-brief-like fit, feel and appearance, which consumers may find appealing. Among the features that give it this fit, feel and appearance are elastic bands about respective leg openings that encircle the wearer's legs. The elastic bands may be formed of, for example, one or more strands or strips of an elastic material such as spandex, bonded with one or more strips of nonwoven or film material to form a band-like elastic strip material. On the subject wearable absorbent article design, these elastic bands are affixed or bonded to the outer surface of a substrate outer cover (backsheet) material, with the lower side edges of each of the elastic bands being substantially coterminous with each of the respective leg openings to create a neatly finished, banded appearance. The elastic strip material may be longitudinally strained prior to affixation to the backsheet material, whereby subsequent relaxation of the elastic strip material causes the backsheet material to gather about the leg openings, for improved fit and comfort.
To date, the subject design has been produced only by hand manufacturing or limited machine-assisted manufacturing techniques, at rates that are too low for economically feasible production of the design as a viable (i.e., competitively priced) consumer product.
Among the problems that the design presents is determining how the elastic strip material can be accurately placed and affixed to the substrate backsheet material at locations required by the design and at economically feasible production speeds, e.g., 450 items or more per minute, in a manner that is reliable, minimizes waste, and maximizes consistency and quality of the band placement and affixing process. It is envisioned that strip material will be applied and affixed to substrate backsheet material at laterally varying design-required locations, as the substrate material moves longitudinally through the manufacturing line at production speed. Under these circumstances, one particular problem lies in determining how to rapidly and repeatedly laterally shift back and forth the point at which such strip material enters a joining/bonding mechanism, without causing the typically pliable, cloth-like strip material to “rope” (longitudinally fold or bunch over on itself) before it enters the joining/bonding mechanism.
A potential associated problem lies in regulating the strain of the elastic strip material as it is affixed to a substrate material. If elastic strip material under longitudinal strain is shifted laterally between two points at which it is gripped, this will cause variation in the strain. Thus, shifting elastic strip material laterally as it is being affixed to substrate material may result in variation in the longitudinal strain of the strip material as affixed to the substrate. In some circumstances this may have undesirable effects.
It would be advantageous if a system, apparatus and method existed to address the problems referenced above.
In one example, the invention may include a strip guide for laterally shifting a longitudinally moving strip material as it enters a joining mechanism that urges the strip material into contact with a moving sheet material, the strip guide comprising a surface over which the strip material passes longitudinally, the surface defining a U-shape.
The dimensions and values disclosed herein are not to be understood as being strictly limited to the exact numerical values recited. Instead, unless otherwise specified, each such dimension is intended to mean both the recited value and a functionally equivalent range surrounding that value. For example, a dimension disclosed as “40 mm” is intended to mean “about 40 mm.”
For purposes of this description, the following terms have the meanings set forth below:
Connected: With respect to a relationship between two mechanical components, unless otherwise specified, “connected” means that the components are directly physically connected to each other, or indirectly physically connected to each other through intermediate components. Unless otherwise specified, “connected” is not meant to imply or be limited to a connection that causes the components to become immovably fixed with respect to each other.
Continuous supply: With respect to a supply of sheet- or strip-like materials forming components of a product, means a length of such material on a roll, or folded accordion-fashion (“festooned”), whereby the material may be drawn therefrom in longitudinal or linear fashion by machinery, to manufacture a quantity of items or products from one such length. Noting that such lengths are not of infinite length, “continuous supply” is not intended to exclude, but also is not intended to necessarily mean, a supply that is infinite or without end.
Downstream: With respect to components of a manufacturing line, relates to the direction or orientation of forward travel of materials through the manufacturing line toward completion of a product.
Lateral (and forms thereof): With respect to the machine direction, means transverse to the machine direction.
Longitudinal (and forms thereof): With respect to a feature of a mechanical system component or component of a product, means substantially parallel to or along the line of the longest dimension of the component.
Machine direction: With respect to a component of a product, refers to any line along the component substantially parallel to the direction of forward travel of the component through the manufacturing line toward completion of a product.
Servo motor: Any rotary electric motor having a rotating output drive shaft, which motor is adapted to be controlled such that the drive shaft can be caused to rotate (within performance limits) at constant, varying and continuously varying, user-selected or user-programmed: angular velocity, angular acceleration/deceleration, rotational direction and/or rotational stop or reversal position.
Strip material: Means any band-like, strip-like, strap-like, or ribbon-like material that, when longitudinally extended, has a greatest longitudinal dimension, and a cross section in a plane substantially perpendicular to the longitudinal dimension, the cross section having an aspect ratio, or a ratio of width to thickness, equal to or greater than about 2.5. The term includes but is not limited to materials that have substantially rectangular or substantially oval cross sections, as well as elongated but irregular cross sections. The term includes but is not limited to materials that are natural or synthetic, cloth or cloth-like, woven or nonwoven, or film, and includes but is not limited to materials that are inelastic, elastic and/or elasticized. The term includes but is not limited to homogeneous strip-like materials, fibrous strip-like materials and assembled or composite strip-like materials, such as laminates or other assemblies of differing materials such as an assembly of one or more elastic strands or strips situated next to one, or between two or more, strips of film, cloth or nonwoven material.
Upstream: With respect to components of a manufacturing line, relates to the direction or orientation opposite that of forward travel of materials through the manufacturing line toward completion of a product.
Example of Wearable Article and Manufacturing Problems Presented
An example of a product such as wearable article 10 as it may be worn by a person is depicted in
In order that they may contribute to the desired fit, feel and appearance, it may be desirable to form waistband 30 and legbands 40 at least partly of an elastic material such as an elastic strip material. The elastic strip material may be formed, for example, by sandwiching one or more strands or strips of elastic polymer material between, for example, two outer strips of nonwoven and/or film. In one example, the elastic strip material may be formed by first longitudinally stretching the one or more strands or strips of elastic polymer material, and then bonding the two outer strips of nonwoven and/or film on either side thereof to sandwich the stretched elastic polymer material therebetween. When the elastic polymer material is allowed to relax it will cause the bonded strips of nonwoven and/or film to ruffle transversely. The resulting transverse rugosities will comprise longitudinally gathered material which accommodates longitudinal stretching along with the elastic strip material. In a particular example, an elastic strip material may be formed of a plurality, for example, three to nine, strands of elastomeric material such as spandex, sandwiched between two outer strips of nonwoven and/or film bonded together, wherein the elastomeric strands are stretched prior to bonding, resulting in an elastic strip material having transverse rugosities of outer material. In another example, an elastic strip material may be formed of a strip of elastic film, or one or more elastic strands, bonded to a single strip of nonwoven or film, on one side only. In another example, an elastic strip material may be formed of a single strip of elastic film material, or single strip of nonwoven material having desired inherent elastic properties.
For purposes of balancing objectives of economy, appearance, fit and comfort, the strip material for the waistband 30 may be, for example, approximately 10-50 mm wide, or approximately 10-35 mm wide, or approximately 10-30 mm wide, or even approximately 10-25 mm wide. Using typical materials, the strip material for the waistband may be, for example, approximately 1-4 mm thick, or even approximately 1.5-2.5 mm thick, in the relaxed and uncompressed state. Thus, the particular strip material used for the waistband may have a cross-section substantially perpendicular to its longest longitudinal dimension, the cross section having an aspect ratio within a broad range of approximately 10:4 (2.5) to 50:1 (50), within a narrow range of approximately 10:4 (2.5) to 25:1 (25), or within any intermediate ranges calculated from the width and thickness ranges set forth above.
For purposes of balancing objectives of economy, appearance, fit and comfort, the strip material for the legbands 40 may be, for example, approximately 10-30 mm wide, or approximately 10-25 mm wide, or approximately 10-20 mm wide, or even approximately 15-20 mm wide. Using typical materials, the strip material for the legbands may be, for example, approximately 1-4 mm thick, or even approximately 1.5-2.5 mm thick, in the relaxed and uncompressed state. Thus, the particular strip material used for the legbands may have a cross-section perpendicular to its longest longitudinal dimension, the cross section having an aspect ratio within a broad range of approximately 10:4 (2.5) to 30:1 (30), within a narrow range of approximately 15:4 (3.75) to 20:1 (20), or within any intermediate ranges calculated from the width and thickness ranges set forth above.
In one example, an elastic strip material of which elastic legbands 40 and/or waistband 30 may be formed may be longitudinally strained prior to being affixed to backsheet 20, and affixed to backsheet 20 while in the strained state. Following affixation to backsheet 20 and completion of the article, relaxation of waistband 30 and/or legbands 40 will cause the waist and/or leg openings in the article to gather so as to fit more snugly and comfortably about the waist and legs of a wearer.
Outer chassis 28 may be formed by cutting the design profile of the outer chassis from a continuous sheet of material having elastic strip material already affixed thereto, in the required locations, in upstream processes.
The present invention might be deemed useful for any purpose that includes applying a strip material to a substrate material in laterally varying locations on the substrate material. Thus, in one example, the present invention may be deemed useful in connection with the location, application and affixation of a strip material to a substrate material to form a product or a portion thereof, such as, for example, partially completed portion 51 (
For purposes such as those described herein it may be desirable that strip material 42 be applied and affixed to substrate backsheet material 50 in a flat condition, which helps provide a leg band that is of uniform width (e.g., the width of the strip) and thickness, and lies flat on the substrate material. It also may be desirable that strip material 42 be applied by a method that minimizes a decrease in applied strip width that may result in “contour error”. Unacceptable contour error may result from laterally shifting a strip material, as it is being drawn through a nip point between rollers, so abruptly that the nip point does not have sufficient time to shift with the lateral movement, such that the strip is drawn askew.
Under certain manufacturing conditions, a pliable strip material may, even under longitudinal tension, exhibit a tendency to longitudinally fold or bunch over onto itself, or “rope,” as machine components shift it laterally at required manufacturing speeds. This problem is believed to be characteristic of relatively pliable strip-like materials. Without intending to be bound by theory, it is believed that for any particular strip-like material, the problem increases along with increasing width-to-thickness ratio (cross-sectional aspect ratio). It is believed that the problem may begin to become significant with pliable materials of the nature discussed herein when they have cross-sectional aspect ratios of approximately 2.5 or greater. As cross-sectional aspect ratio for a given material increases, the problem becomes more significant. It is believed that the problem also becomes more significant with increasing pliability across the width of the material (increasing flexibility along longitudinal lines). It is also believed that the problem becomes more significant with a decrease of longitudinal tension in the material. Additionally, air resistance/friction may contribute to roping when attempting to rapidly shift a free span of strip material laterally through open air at required manufacturing speeds. If a free span of pliable strip material is shifted laterally at high enough speeds through open air, friction with the air may cause the span to twist and/or rope erratically. If strip material 42 is roped as it enters a joining mechanism to be affixed to backsheet material 50, non-uniform leg bands having defects in width, thickness, placement, feel and/or appearance are among several possible undesirable results.
A combination of manufacturing line components including a guide upstream of a joining mechanism that urges and affixes a strip material and a substrate sheet material together, is described below. The components also may include a mechanism for regulating the strain in the strip material as it enters the joining mechanism. It is believed that components in the combination, and the combination, are embodiments of components and a system that may be effective at continuously affixing strip material to substrate sheet material at laterally varying locations relative to the machine direction, at speeds that may be required for manufacturing, while reducing or avoiding the problem of roping of the strip material described in more detail above. Embodiments of the strain regulation mechanism described may enable effective regulation of the strain in the strip material as it is affixed to the substrate sheet material.
Example of Combination of Manufacturing Line System and Components for Locating and Affixing Strip Material to Sheet Material
Coupling collar 109 may be mounted to the end of drive shaft 151 in any suitable manner that prevents substantial rotational slippage/movement of strip guide arm 100 relative to drive shaft 151, including, for example, by welding, press-fitting, keying, splining, set screw(s), etc. However, welding and other devices for mounting that involve potential alteration, modification, damage or destruction to draft shaft 151 and/or servo motor 150 may in some circumstances be deemed undesirable for reasons that may include added complexity and expense of system assembly, and potential complication or frustration of replacement of a worn or broken strip guide arm 100 without having to also repair or replace servo motor 150. Devices such as set screws may be unreliable in that stress and vibration during operation may cause them to work loose or fail. Thus, one example includes a taper locking collar as a device for mounting coupling collar 109 to drive shaft 151. A suitable example of such a taper locking collar is a TRANTORQUE keyless bushing available from Fenner Drives, Leeds, UK.
Examples of suitable servo motors include servo motors designated MPL-B330P and MPL-B4560F, available from Rockwell Automation, Inc., Milwaukee, Wis. The programming of the selected servo motor, to effect lateral location of the strip material 42 relative to backsheet material 50 and create the partially completed portion 51, will be directed by the particular article design.
A strip guide 102 may be situated at a downstream location on strip guide arm 100. The components may be arranged such that strip guide 102 is upstream of a joining mechanism 200. In the example shown in
A joining mechanism utilizing compression as the primary means of creating bonds, such as, but not limited to, the mechanism described in the aforementioned patents, provides bonding of respective sheet-like or strip-like polymeric materials through rapid compression of the respective materials together beneath the protuberances, along the roller nip line. Without intending to be bound by theory, it is believed that rapid compression beneath the protuberances causes the respective materials to be rapidly deformed and partially expressed together from beneath the protuberances, to form structures of entangled or combined material beneath and/or around the protuberances. Welds or weld-like structures at or about the protuberances result. In some circumstances compression bonding provides advantages, including relative simplicity and cost effectiveness. It may reduce or eliminate the need for more complex joining and bonding systems that rely upon, for example, adhesives and mechanisms to handle and apply them, or weld-bonding systems that require a heat source, ultrasonic wave source, etc. Without intending to be bound by theory, it is believed that these advantages are substantially independent of variations in line speeds in at least some circumstances, including line speeds within currently known economically and technically feasible ranges for manufacture of disposable diapers and training pants.
The one or more servo motors 150 may be situated such that the arc paths of strip guides 102 occurs within in one or more planes. If the components are arranged such that the arc path of a strip guide 102 is substantially parallel with the plane which contains the nip line between joining rollers 201, 202, one mode of variation in the angle at which the strip material enters the nip is eliminated. Without intending to be bound by theory, it is believed that control over lateral shifting of the strip material and/or avoidance of roping are simplified and/or improved by such an arrangement.
Strip Guide and Guide Arm
An example of a strip guide 102 is depicted in perspective, side, front and rear views in
In the example shown, strip guide 102, strip guide arm 100, and coupling collar 109 may be formed of aluminum alloy, and also may be integrally formed. Materials having a relatively high strength-to-weight ratio may be desirable in some circumstances. Examples of other suitable materials may include engineering plastics (such as polycarbonate thermoplastics, for example, LEXAN), aluminum, titanium alloys, thermoplastic or thermosetting resins reinforced with carbon fibers, graphite fibers, polyamide fibers, metal fibers and/or glass fibers, or other carbon fiber, graphic fiber, polyamide fiber, metal fiber and/or glass fiber composites.
Still referring to
Without intending to be bound by theory, it is believed that a strip guide such as strip guide 102 having strip edge guides such as those shown at 106 a, 106 b (
As shown in the examples depicted in
The upstream and downstream strip insertion gaps 111, 108 provide for ease of lateral insertion of the strip material to be used into and along strip guide arm 100 during set-up. In another example, however, the respective strip retainer extensions 110 may be formed to meet, or be continuous to effectively constitute a single retainer structure, whereby the strip material must simply be longitudinally threaded thereunder, rather than laterally inserted through a gap, at set-up. Similarly, strip edge stops 105 a, 105 b (
As previously noted, without intending to be bound by theory, it is believed that a strip guide 102 may be more effective than other embodiments for the purposes contemplated herein if it includes an intermediate portion 103 (see, e.g.,
Additionally, without intending to be bound by theory, it is believed that a strip guide 102 may be more effective if it has at least one side portion 104 a and/or 104 b joining the intermediate portion 103, than other possible embodiments not having such a side portion, for purposes such as those described herein. A side portion joining the intermediate portion at a side opposite the direction of lateral motion of the strip guide may provide additional guiding surface against which a strip material may ride during abrupt and/or severe changes in lateral position of the strip guide. The side portion may be substantially straight, and may be of a length that is approximately 21-61 percent of the width of the strip material, or approximately 26-56 percent of the width of the strip material, or approximately 30-52 percent of the width of the strip material, or even approximately 32-50 percent of the width of the strip material to be used. It is believed that such a dimension causes optimization of the orientation of the respective longitudinal side edges of a strip as it enters the nip between a roller pair, striking a balance between most effective control over lateral shifting and minimizing the likelihood of roping and contour error.
It is further believed that embodiments having two such side portions are more effective than embodiments with only one side portion, particularly if the strip material is to be shifted laterally to both sides of a line of entry of the strip material at the upstream end of the strip guide arm 100 (e.g., at upstream entry point 113). Expressed differently, when strip guide 102 is to move back and forth to points on both sides of the line of entry of the strip material at upstream entry point 113, two such side portions 104 a, 104 b may be desirable in some circumstances to improve control over the strip material.
During operation, as the strip guide 102 moves toward the limit of its lateral arc path to shift the strip laterally, the strip exits the strip guide at an increased lateral angle, creating a potential for friction lock, i.e., a point of unacceptably concentrated friction between the strip and the strip guide at the exit point as a result of tension in the strip. To mitigate this problem, in addition to having the above-described features, it may be desirable in some circumstances to shape the inside distal edges of the strip guide 102. The inside distal edges may be shaped such that they are chamfered, rounded or radiused, or even given a quarter-round transition, from inside surface to outside edge, to reduce friction between the strip guide 102 and the strip material as it passes longitudinally therethrough and exits the downstream end.
As noted, in the example shown strip guide 102 may be integrally formed with strip guide arm 100. Referring to
Additionally, a trough or other channel, conduit, tube or other suitable containing, retaining and/or shielding structure along strip guide arm 100 may serve to shield the strip material from surrounding air and the resistance to lateral movement of the strip material 42 therethrough. Absent a shielding structure, friction with surrounding air may cause a free span of a typically pliable and relatively light, cloth-like strip material 42 to erratically and uncontrollably flip about and rope as the strip material is rapidly shifted laterally by strip guide 102.
In another example of a possible alternative to the upstream strip entry point 113 depicted in the Figures, the strip guide arm may have a upstream strip entry guide similar in design to the strip guide 102 but oriented in the opposite direction. This may provide further assurance against roping of the strip material. It also may serve to prevent or reduce increased friction or binding at the entry of strip material 42 into/onto strip guide arm 100 when strip guide arm pivots and introduces a varying angle in the path of the strip material, about the strip entry point. Again, avoidance or reduction of a concentration of friction at any particular point is desirable to avoid inconsistencies in the longitudinal strain of the strip material 42 as it is drawn into the joining mechanism.
It may be desirable in some circumstances that one or more of the surfaces of the strip guide 102, and other surfaces in or along strip guide arm 100 that contact the moving strip material, be polished to reduce friction between the strip material and such surfaces. This may include any of the inner surfaces of trough 101, strip edge stops 105 a, 105 b, strip edge guides 106 a, 106 b, strip entry point 113, strip retainer extensions 110, and any intermediate strip-contacting structures.
In addition, or as another possible measure, one or more of these surfaces may be coated with a low-friction coating, such as, for example, a fluoropolymer-based coating such as TEFLON, a product of E.I. du Pont de Nemours and Company, Wilmington, Del. Relative to the coefficient of friction provided by the strip guide/strip guide arm material without a coating, any suitable coating that lowers the coefficient of kinetic friction with the material of the outer surfaces of the strip material to be used may be selected. In another example, where an adhesive is to be applied to the strip material upstream of the strip guide arm 100 and/or strip guide 102, it may be desirable to coat strip-contacting surfaces of the strip guide arm 100 and/or strip guide 102 with an adhesive release coating. In another example, one or more inserts of a low-friction material conforming to the desired strip-contacting surface shape may be affixed on or within strip guide 102, strip guide arm 100, trough 101, strip edge stops 105 a, 105 b, strip edge guides 106 a, 106 b, strip entry point 113, strip retainer extensions 110, and any intermediate strip-contacting structures. Such inserts may be formed in whole or in part of low-friction materials such as, but not limited to, nylon, high density polyethylene, and fluoropolymer-based materials such as TEFLON.
In another example, a strip guide arm 100 and strip guide 102 may have some or all of the features and spatial arrangement with respect to a joining mechanism 200 as described above. However, rather than being connected to a servo motor, strip guide arm 100 may be connected at a pivot point to a stationary component, about which pivot point the strip guide arm 100 may pivot back and forth. In this example, strip guide arm 100 also may include a cam follower as part thereof, or connected thereto, which rides on a rotating cam directly or indirectly driven by a rotating driving mechanism, such as a rotary electric motor. The cam follower may be urged against the cam by any appropriate biasing mechanism, such as, but not limited to, one or more springs. The cam may be formed to have a profile such that by its rotation, strip guide arm 100 pivots as required to laterally shift strip material as required for the article being manufactured. The rotating driving mechanism may be operated so as to rotate the cam at a speed which is suitably associated with the speed at which the substrate material is moving.
In another example, a strip guide 102 having some or all of the features described above may be employed without a strip guide arm, servo motor, or the rotary operation described above. Rather, a strip guide may be connected to a linear movement mechanism such as, for example, a linear motor or actuator arranged to move the strip guide 102 along a line upstream and substantially parallel to the nip line between joining rollers 201, 202.
Additional Strip Guide Design Features; Strip Guide Arm Dimensions, Location and Orientation
As the arranged distance between the distal edge of strip guide 102 and the nip line is decreased as constraints permit, it may become desirable in some circumstances to form strip guide 102 so as to have a radiused concave profile as viewed from a side, having radius r3 (see
Under certain circumstances forces created by air entrainment or other factors may tend to lift strip material 42 from the inner surfaces of strip guide 102, reducing the efficacy of strip guide 102. Still referring to
In some circumstances it may be desirable that the length of the strip guide arm 100 is as great as possible. As the strip guide arm 100 is made longer, the arc path of the strip guide 102 in front of nip line 206 approaches that of a line. As such a linear path is approached, the potential sharpness of a lateral shift of the strip material in front of the nip line is increased. However, the torque load capacity of any servo motor, and the material strength of any strip guide arm, will have limits. These factors are sources of constraints on the design length of the strip guide arm 100. Torque load on the servo motor in the arrangement of components described herein will be at its maximum when the most rapid change in direction and/or speed of rotation (highest angular acceleration/deceleration) is imposed by the design of the finished product (i.e., the most abrupt angular acceleration/deceleration required of the strip guide arm will impose the greatest torque load). If the torque load capacity of a servo motor is exceeded, the precision of rotation of the servo motor drive shaft may deviate unacceptably from that required by the associated programming, and the servo motor may even fail. Additionally, as a strip guide arm 100 mounted to the drive shaft of a servo motor is made longer and/or heavier along its length, angular inertia and angular momentum become greater. As a result, angular acceleration/deceleration require greater torque, imposing greater demand on the servo motor. Bending/shear stress along the length of the strip guide arm also increases with increasing angular acceleration/deceleration and angular inertia/momentum, increasing the probability of strip guide arm material failure. Related constraints are imposed by the line speed and the resulting cycling speed demanded of the servo motor, and by the magnitude and abruptness of the change in lateral placement of the strip material, a function of the design of the article being manufactured. Another related constraint is imposed by the weight of the strip material that is being handled by the strip guide arm, which adds to lateral inertia and momentum which must be overcome to effect lateral shifting. Many or all of the above-discussed design considerations will be affected by the particular design of the article to be manufactured, which will involve a particular profile of location and affixation of a strip material to a substrate material at laterally varying locations on the substrate material.
Effects of Described Components and Features
Certain effects and advantages provided by components and features described above are discussed with reference to
Thus, a system having one or more of the features described above may be used to manufacture a portion of wearable article such as that shown in
Strip Strain Regulation
As previously noted, in one example of a design of a product such as wearable article 10 and the manufacture thereof, the design may call for the longitudinal straining of the strip material prior to the affixing thereof to a substrate sheet material. In some circumstances it may be desirable to provide a system for introducing and regulating the amount of strain of the strip material prior to its entry into a joining mechanism.
An example of a strain regulation system is schematically depicted in
To longitudinally strain incoming strip material 42 prior to bonding to incoming backsheet material 50, feed rollers 301, 302 may be caused to rotate at a speed whereby the linear speed of the circumferential surfaces of feed rollers 301, 302 is slower than the linear speed of the circumferential surfaces of joining rollers 201, 202 of joining mechanism 200. If r1 is the radius of feed roller 301 (in meters) and ω1 is the rate of rotation of feed roller 301 (in rotations/second), the linear speed V1 of its circumferential surface is:
Similarly, if r2 is the radius of joining roller 201 (in meters) and ω2 is the rate of rotation of joining roller 201 (in rotations/second), the linear speed V2 of its circumferential surface is:
Strain will be introduced into the strip material 42 if V1 is less than V2 and strip material 42 does not substantially slip longitudinally as it passes through the respective nips between respective roller pairs 301, 302 and 201, 202. Thus, referring to
Thus, if a design for an article calls for longitudinally straining the strip material to strain ε(ε=change in length/relaxed length; where ε is expressed as a percentage) prior to bonding to the substrate material, relative speeds V1 and V2 will provide for the required strain ε if:
In the event, however, that the length of the path of the strip material from the feed mechanism to the joining mechanism is subjected to change, strain of the strip material in zone “B” will undergo an associated transient elevation or dip. If the change in path length is substantial and abrupt enough, it is possible that the strain in the strip material may be caused to transiently elevate or dip substantially. Examples of a system as described herein shift a strip material path laterally prior to its entry into a joining mechanism, to cause affixation of the strip material to a substrate material in laterally varying locations on the substrate material. This lateral shifting causes change in the length of the path of the strip material from the feed mechanism to the joining mechanism. A change of this nature may be substantial and abrupt enough to substantially vary strain of the strip material in zone “B”.
Pivoting of strip guide arm 100 by an angle θ causes an increase in the path length. The increase reaches an initial peak in the path length, which approaches the sum of strip guide arm length L plus the distance d1 from strip guide displacement point D to first nip point 206 a, as speed of rotation by angle θ approaches infinity (pivoting of arm 100 approaches instantaneous). The increase then settles back from the initial peak to a second path length, as the nip point between joining rollers 201, 202 shifts as indicated by the arrow in
With V1 and V2 held constant, a path length increase will not necessarily cause a substantial elevation in strain. Through the continuous feeding and drawing of strip material through zone “B” by roller pairs 301, 302 and 201, 202, the system continuously corrects an elevation or dip in strain, always asymptotically seeking the strain determined by the values of V1 and V2 (see equations immediately above). Accordingly, in some circumstances the system may effectively regulate and maintain substantially consistent strain despite changes in path length. The time required for the system to substantially correct a transient elevation in strain resulting from an increase in path length is dependent upon the total length of the strip material path in zone “B” and the values of V1 and V2. Thus, if pivoting of strip guide arm to angle θ is relatively slow and gradual, the system may be able to effectively “keep up,” continuously seeking initial strain, and any transient elevation in strain may be relatively slight.
As the pivoting of strip guide arm by angle θ becomes more rapid, however, the system may become unable to effectively “keep up” and maintain strain within an insubstantial margin of elevation over initial strain. Thus, it is possible that a relatively rapid pivoting of strip guide arm through angle θ may cause a substantial elevation in the strain of strip material in zone “B”.
The foregoing describes only one possible example of circumstances in which strain in strip material 42 may vary as a result of a change in pivot angle θ. There may be other circumstances in which elevations and even dips in strain may be caused. For example, still referring to
One example of the potential effect of such a transient elevation in strain is explained with reference to
Following such application, strip material 42 may be allowed to relax. Elastic strip material 42 will seek to return to its relaxed length Ls, and the affixed backsheet material 50 will develop transverse rugosities 22, along strip material 42 as depicted in
If, however, the strain in strip material 42 is varied as it is being affixed to the backsheet material, the unruffled length LB of backsheet material 50 may not be evenly distributed along the relaxed length of strip material 42 after affixation, and relaxation. For example, referring to
In some circumstances involving such variation in strain, the linear quantity of backsheet material gathered along strip material in a first region, per relaxed unit length of strip material, may be, for example, approximately 125 percent, approximately 150 percent, approximately 175 percent, approximately 200 percent, or even more, than that in one or more adjacent regions. This may evidence that the strain of the elastic strip material as it was applied to the substrate material with the substrate material in flat, unruffled condition, was greater in the first region than in the one or more adjacent regions, by roughly corresponding percentages. In a product such as a finished wearable article wherein the strip material encircles a leg opening, this may manifest itself in a discontinuity or variation in the gathering of material about a leg opening.
Referring again to
Such compensation may be provided by use of a feed servo motor 350 driving one or both of feed rollers 301, 302. In one example, one of feed rollers 301, 302 may be driven by a feed servo motor, and the other of feed rollers 301, 302 may be a passive, idling roller. Referring to
For example, while angle θ is increasing, the strip path length is growing and V1 may be temporarily increased in accordance with the rate of increase in the path length, which can mitigate or avoid an unacceptable elevation in strain of strip material 42 in zone B.
At any time period in which angle θ may dwell at a relatively constant value (as may be required by a particular article design), the strip path length also becomes constant, i.e., the rate of increase or decrease in the path length in zone “B” becomes zero. In this event the system would cause strain in the strip material to approach the strain determined by the initial values of V1 and V2, and V1 may be returned to its pre-adjustment initial value to maintain substantially constant strain of the required design (initial) value.
If after a dwell and substantial stabilization, angle θ decreases from a peak value abruptly enough to cause an unacceptable dip in strain below initial design value, a compensating adjustment may be made. Thus, while angle θ decreases from a peak, V1 may be temporarily decreased in accordance with the rate of decrease in the path length, which can mitigate or avoid an unacceptable dip in the strain of strip material 42 in zone B.
The requirement for such correction, and the programming of the feed servo motor 350 driving feed rollers 301, 302 to regulate strain in the manner described above, will be directed by factors including the design features and specifications of the particular product being manufactured, the speed of the joining mechanism 200 and/or rollers 201, 202, the programming of servo motor 150, the distance between the feed nip and the upstream strip entry point 113, the length of the strip guide arm 100, and the distance between the distal end of strip guide 102 and joining nip line 206.
A strain regulation/adjustment mechanism such as the example described above may be used for purposes other than maintenance of consistent strain. There may be circumstances in which it is desirable to intentionally vary strain. For example, referring to
Every document cited herein, including any cross-referenced or related patent or application, is hereby incorporated herein by reference in its entirety unless expressly excluded or otherwise limited. The citation of any document is not an admission that it is prior art with respect to any invention disclosed or claimed herein or that it alone, or in any combination with any other reference or references, teaches, suggests or discloses any such invention. Further, to the extent that any meaning or definition of a term in this document conflicts with any meaning or definition of the same term in a document incorporated by reference, the meaning or definition assigned to that term in this document shall govern.
While particular embodiments of the present invention have been illustrated and described, it would be obvious to those skilled in the art that various other changes and modifications can be made without departing from the spirit and scope of the invention. It is therefore intended to cover in the appended claims all such changes and modifications that are within the scope of this invention.